Does this EP offer audio upgrade to the BBC tracks?
What BBC tracks are you referring to? They have not been officially released on John Mayall's "Live at the BBC" (DECCA 984 466-5) nor on any other official album as far as I know.
This is the information on the recording provided by the publisher:
"John Mayall´s Bluesbreakers – Broadcast 65 EP
In November 1965, Jack Bruce briefly stood in for John McVie on bass in John Mayall's Bluesbreakers, making a lasting impression on Eric Clapton, who later said of Bruce, 'it was his obvious desire to make the most out of every musical opportunity.... The music, and the experience of playing it, took me to another dimension'. This line-up recorded a live album at the Flamingo, which was scrapped because the quality of the tape was poor. Here though is aural evidence of their early collaboration from a 1965 radio broadcast. Side One: Hideaway (King), Little Girl (Mayall), Side Two: Tears In My Eyes (Mayall), Parchman Farm (Allison)."
The back cover of the EP, however, says the songs stem from live broadcasts made in 1966...
In the IORR "Tell Me" section, rgutter notes:
I noted in another forum that
[*] This is a February 9 1966 BBC Radio Jazz Beat performance.
[*] Jack Bruce had been gone for a couple of months.
[*] The Flamingo recording was never intended for release.
Well, I've got a private/bootleg (?) compilation of "John Mayall and the Bluesbreakers Featuring Eric Clapton" called "Bluesbreaking!" (3BR 129) that includes all the 4 tracks in question and gives the following information:
Hideaway, Little Girl, Tears in My Eyes: Recorded 9 February 1966 and broadcast 12 February 1966 on the BBC "Jazz Beat" programme
Parchman Farm: Recorded 25 October 1965 and broadcast 30 October 1965 on BBC's "Saturday Club"
...and according to that bootleg it's not Jack Bruce but John McVie playing bass.
So it seems that the information on the EP is wrong.
Soundwise the quality of the EP is not superior to those of the "Bluesbreaking!" tracks.
Hope that helps...